1. Field of the Invention
This invention relates to an apparatus for measuring the eccentricity of an aspherical surface that facilitates the measurement of the amount of eccentricity of an aspherical lens and a method for measuring the same.
2. Description of Related Art
Optical lenses using aspherical surfaces have come to be widely applied. Since it is very difficult that aspherical lenses are configured by grinding, molding methods using molds are popularized. However, the face-to-face eccentricity of the aspherical lens is caused by an insufficient adjustment of the mold in molding, and the aspherical lens undergoes the degradation of optical performance when optical modules are finally assembled. Consequently, for the purpose not only of improving the optical performance, but also of readjusting the mold in molding, a measuring device measuring the eccentricity of the aspherical lens after molding, is essential.
A conventional apparatus for measuring the eccentricity of the aspherical lens is set forth, for example, in Japanese Patent Kokai No. Hei 07-229811.
In a method for measuring the eccentricity that uses this apparatus, the coordinates of an aspherical surface to be examined, of the aspherical lens are measured at a plurality of places to perform fitting of a measured result to design data of a virtually decentered aspherical surface to be examined so that the eccentricity of the aspherical surface is determined from the amount of eccentricity that a difference between both is minimized.